On March 22nd, I will be participating in the Prairie Spirit 100, a 100-mile race in Ottawa, Kansas. The course is completely flat and features a crushed granite surface, which is very easy on the joints.
Yesterday, I completed a solid 50k, with half of the distance on that nice granite surface and the other half on sidewalks. My finishing pace was 14 minutes per mile, which aligns perfectly with my goal for the 100-mile race. If I maintain that pace, I would finish in about 23 hours and 20 minutes, which I would be very happy with!
These self-supported ultras tend to take a little longer since I have to manage all my own aid stations, refilling water and supplies on my own. In organized races, you typically receive assistance with that, which is definitely a nice benefit.